In a known manner, a power converter comprises several input phases connected to the network, for example three input phases if it is connected to a three-phase network. Connected to its input phases, a power converter comprises a rectifier stage making it possible to transform the AC voltage provided by the network into a DC voltage. The converter also comprises a power supply bus fitted with a first power supply line with positive potential and with a second power supply line with negative potential and to which lines the DC voltage is applied and a bus capacitor connected between the first power supply line and the second power supply line and intended to maintain the DC voltage on the bus constant.
When the rectifier stage is connected between an AC network and a capacitive load, such as for example the DC power supply bus of a variable speed drive, the input current drawn from the network is formed of spikes corresponding to the recharging of the bus capacitor as soon as the voltage between input phases (AC) becomes greater than the voltage of the power supply bus (Vbus). Whether the rectifier stage is single-phase or three-phase, the input current drawn from the network is therefore far from being sinusoidal since, in addition to its fundamental, it contains numerous harmonics. The input current Ie drawn from the network is therefore defined by a fundamental current to which are added harmonics whose amplitude can be expressed as a percentage with respect to the fundamental current.
The harmonics of the input current Ie are characterized by two known indicators dubbed THDi (“Total Harmonic Distortion of Current”) and PWHD (“Partial Weighted Harmonic Distortion”). The THDi corresponds to the harmonic current distortion ratio which represents the rms value of the harmonics relative to the rms value of the fundamental current. For its part, the PWHD introduces a weighting giving extra weight to the high-frequency harmonics, more particularly those of orders 14 to 40.
A power converter connected to a three-phase network must satisfy the IEC61000-3-12 standard imposing a limit value for the indicator THDi, a limit value for the indicator PWHD as well as limit values for the harmonics of order 5, order 7, order 11 and order 13 of the input current.
According to this standard, for an RSCE of greater than 350:                the THDi must be less than 48% of the fundamental current,        the PWHD must be less than 46% of the fundamental current,        the harmonic of order 5 must be limited to 40% of the fundamental current,        the harmonic of order 7 must be limited to 25% of the fundamental current,        the harmonic of order 11 must be limited to 15% of the fundamental current,        the harmonic of order 13 must be limited to 10% of the fundamental current.        
In a known manner, the RSCE characterizes the nominal apparent power of the converter with respect to the short-circuit power of the network to which the converter is connected.
A known solution for reducing the THDi is to perform a filtering on the DC bus through the addition of a DC inductor, which, if its value is sufficiently large, ensures continuous conduction, that is to say the rectifier current Ired flowing on the bus, as output from the rectifier, never drops back to zero. The larger the value of the inductor employed, the less the ripple in the rectifier current Ired. If the value of the DC inductor tends to infinity, the rectifier current becomes constant and there is no longer any ripple in the DC bus voltage since it is stabilized at the mean value of the rectifier voltage Vred. To obtain a rectifier current Ired which is as constant as possible, the value of the inductor will therefore have to be very high, and this will give rise to cost and bulkiness problems.